Keywords

Introduction

Pressure and flow triggering have improved greatly in the new generation of ventilators. The routine use of one or the other in adult patients in the ICU setting is not yet well established.

Objective

To compare the use of two trigger systems, pressure or flow, during pressure support ventilation on the respiratory parameters of ICU mechanically ventilated patients.

Methods

We prospectively evaluated 20 mechanically ventilated adult ICU patients recovering from acute respiratory failure that could be ventilated with pressure support of 15 cmH2O, PEEP of 5 cmH2O and FIO2 of 40%. The patients were ventilated by two different trigger systems during pressure support ventilation: a flow trigger of 2 l/min or a pressure trigger (-2 cmH2O) during pressure support ventilation. We measured the respiratory rate (RR), expiratory tidal volume (VTe), minute ventilation (MV), VCO2, VTCO2, ETCO2, SpO2, mean arterial pressure (MAP) and heart rate (HR) after 15 minutes in each study situation.

Results

The respiratory and hemodynamic variables measured with the two different trigger systems during pressure support ventilation are presented in Table 1.

Table 1

Respiratory and hemodynamic variables measured with two different trigger systems

Trigger

Cycling-off (%)

RR (beats/min)

VTe (ml)

MV (l/min)

VCO2 (l/min)

VTCO2 (l/min)

ETCO2 (l/min)

SpO2 (%)

MAP (mmHg)

HR (beats/min)

2 F

25%

17.3

582

9.4

181.4

11.37

28.4

98.7

96.9

83.2

-2 P

25%

17.9

573

10.3

195.1

11.55

28.5

98.6

93.8

83.3

P value

0.38

0.56

0.03

0.14

0.72

0.77

0.19

0.08

0.88

Conclusion

During the pressure trigger ventilation the minute ventilation was greater than that in the flow triggering ventilation without affecting the other ventilatory parameters.